[Field of the Invention]
The present invention relates to a vehicle transmission system, and more particularly, to a transmission mechanism that changes (performs a gearshift operation) a gearshift position using a driving force of an actuator and a control unit that controls the actuator.
[Description of the Related Art]
As one of vehicle transmission mechanisms of the prior art, a manual transmission mechanism that changes a gearshift position (performs a gearshift operation) by manually manipulating a selector by a driver is known in the art. For example, the manual transmission mechanism has a driveshaft, a slide gear provided slidably along a driven shaft, a shift fork that makes a sliding operation of the slide gear, and a shift cam rotated to move the shift fork. In addition, as a driver manually manipulates the selector, the shift cam is rotated, and the shift fork is moved in response to the selector manipulation, so that the slide gear slides. As a result, the gearshift position is changed. A gearshift position of the manual transmission mechanism is determined depending on the rotational position (rotation angle) of the shift cam.
The manual transmission mechanism has a feeding mechanism that automatically rotates the shift cam up to a predetermined rotational position. As a result, even when a driver unskillfully manipulates the selector, it is possible to reliably change the gearshift position and hold the changed gearshift position. In Japanese Laid-open Patent Publication No. 2005-127392, a feeding mechanism for the manual transmission mechanism provided with a shift stopper plate and a shift stopper arm is discussed. The shift stopper plate is rotated in synchronization with the shift cam and has a plurality of approximately triangular toothed portions arranged side by side in a circumferential direction (that is, in a rotational direction) on its outer periphery. The shift stopper arm which is swingable or reciprocatable has a roller provided in its tip and biased by a biasing member such that it is inserted into a concave portion between toothed portions of the shift stopper plate. In this configuration, even when a driver stops the shift cam in a position where the roller is not perfectly inserted into the concave portion, the roller of the shift cam is automatically rotated into a position inserted into the concave portion by virtue of the biasing force of the biasing member. For this reason, it is possible to reliably change a gearshift position and hold the changed gearshift position.
On the other hand, an automated manual transmission (AMT) mechanism is known as a mechanism having both excellent power transmitting efficiency of the manual transmission mechanism and convenience of the automatic transmission mechanism. The AMT mechanism has an actuator such as a motor and changes the gearshift position by rotating the shift cam using a driving force of the actuator. The AMT mechanism has a gearshift holding mechanism for holding the gearshift position. The gearshift holding mechanism has a configuration similar to that of the feeding mechanism of the manual transmission mechanism. For example, as discussed in Japanese Utility Model No. 3159206, those having configurations similar to that of the manual transmission mechanism are employed in the shift stopper plate of the AMT mechanism.
Patent Document 1: Japanese Laid-open Patent Publication No. 2005-127392
Patent Document 2: Japanese Utility Model No. 3159206
If the toothed portion of the shift stopper plate has an approximately triangular shape, it is necessary to increase output power of the actuator until the shift stopper arm climbs over the toothed portion of the shift stopper plate. Meanwhile, if the shift stopper arm climbs over the toothed portion of the shift stopper plate, the torque necessary to rotate the shift cam is abruptly reduced. For this reason, it is necessary to abruptly reduce the output power (rotation torque) of the actuator or set it to zero immediately after the shift stopper arm climbs over the Loathed portion of the shift stopper plate. This makes the control difficult. In addition, if the toothed portion of the shift stopper plate has a shape similar to that of Japanese Laid-open Patent Publication No. 2005-127392 or Japanese Utility Model No. 3159206, a significant torque is necessary to allow the shift stopper arm to climb over the toothed portion of the shift stopper plate. This increases a load of the actuator.